A thin filler nozzle for my air pump. My kids promptly lost the one that came with it and then needed a ball inflated. This was 5 minutes of CAD at OnShape.com. I printed with 100% infill and fairly low layer height. Supports around the flange helped, too. To get the a threaded version, visit the OnShape.com link above and select all the crossed off features, right click, and "unsupress".